Acoustic neuroma

What is an acoustic neuroma?

An acoustic neuroma is a benign tumour that arises from the nerve of balance as it passes between the inner ear and the brain. This nerve is called the vestibular nerve, and the cells that the tumour arises from are called Schwann cells. These cells normally form the insulation around the nerve, like the plastic coating around an electrical cable. The other name for an acoustic neuroma is a vestibular schwannoma – you may find either name used but they are both referring to the same thing.

In this sense the word “benign” refers to a tumour that will not spread elsewhere in you brain or body. Acoustic neuromas can however, if left undiagnosed and untreated, grow to the extent that they can put pressure on the brain and cause serious harm.

Who gets an acoustic neuroma?

Acoustic neuromas most commonly affect men or women over 40, but can be found as early as the age of 10. They are very rare tumours – we would expect to see only 10 to 20 new diagnoses a year from a population of one million people.

Having tumours on both sides is exceptionally rare, and is a defining feature of a genetic condition called neurofibromatosis type 2.

What causes acoustic neuromas?

Apart from the link with neurofibromatosis the cause is unknown. Research is being carried out into the possible causes. Many patients ask if there is a link with mobile phone use. To date there has been no strong evidence that this is the case.

What are the symptoms and signs of an acoustic neuroma?

The nerves of hearing and balance (cochlear and vestibular nerves) lie very close to each other. Most patients with an acoustic neuroma will have suffered one or more of tinnitus (buzzing or ringing in the ears), hearing problems or problems with their balance. Because the tumours tend to grow very slowly, these symptoms may have developed gradually over several years. Also, many patients experience surprisingly little in the way of dizziness or balance problems as their brain will have adapted to the gradual loss of balance information from one inner ear.

The nerve that controls the muscles of the face (facial nerve) also runs very close to the balance nerve. However it is comparatively rare for the tumour to affect this nerve. Possible signs would be facial twitching, or facial weakness or drooping, much like a Bell’s palsy.

Larger tumours may affect the nerve that collects sensory information from the face (trigeminal nerve). Pressure on this may cause facial tingling, numbness or pain.

Very large tumours may press on a part of the brain called the brainstem. This can cause problems walking or very rarely headaches.

Some of the effects of the tumour are likely to be irreversible. For instance once hearing has gone, it will not return, whatever treatment option is chosen. However some of the other effects of the tumour may be treatable. It is important that you discuss this point with the doctors looking after you.

Why will I be seen at Hurstwood Park?

At Hurstwood Park we look after people with a wide range of neurological problems. We see patients diagnosed with acoustic neuromas from a population of about 2 million people, covering most of Sussex and parts of Surrey and Kent.

It is likely that you will be seen in what we call our “skull base” clinic. In this clinic you mayl meet a number of different people, including neurosurgeons and ear, nose and throat surgeons. We have close links with a wide range of other specialist doctors, physiotherapists and nurses, some of whom may be involved in different aspects of your care.

What tests and investigations will I need?

You will almost certainly have already had at least one MRI scan to make the diagnosis. Further MRIs may be required. You will probably need to have some hearing and balance tests carried out in the audiology department at the Royal Sussex County Hospital in Brighton. We will organise these for you.

What treatment options are available?

Broadly speaking, the options are observation, radiotherapy or surgery.

There are a number of factors that will taken into account when deciding which treatment will be best for you. These include the size of the tumour, how much you are experiencing in the way of symptoms and, very importantly, your own preferences. Sometimes there will be no clear answer as to which is best and more than one option will be perfectly valid. There will be plenty of time at your clinic visit to discuss this.

Observation

If the tumour is small and not causing you significant problems, we may decide to observe the tumour rather than treat it straight away. This will involve having scans at Hurstwood Park on a regular basis. Your first scan will probably either be after 6 or 12 months, and then annually. Our specialist radiologists will be able to compare the scans with previous ones to see if the tumour shows any signs of growth. If it does then we may need to consider either radiotherapy or surgery. If not we will probably increase the time between scans after 2 to 3 years of observation.

What are the benefits of observation?

We know from published studies that a large number of tumours- probably over half- show no significant growth if observed for many years. This means that we may be able to put treatment off for a long time, or avoid it altogether. If the tumour does grow it is likely to do so only very slowly, which is why we will leave it for six months or a year until your first repeat scan.

What are the disadvantages of observation?

A policy of observation does mean regular hospital attendances for scans and follow-up visits for the foreseeable future. Some patients have difficulty coming to terms with the uncertainty that comes with this approach and would rather get on and have treatment. This is very much a personal decision and one with which the team will help you.

The medical risks of adopting a policy of observation are small. If the tumour grows, it is likely to do so very slowly. Growth is likely to be detected early, before the tumour can cause serious problems. There is however a chance that during the period of observation your hearing will deteriorate. This can happen whether the tumour grows or not. Approximately half of patients under observation will experience significant loss of hearing within 5 years.

If we do detect that the tumour is growing we will most probably need to consider treating it.

Surgery

Surgery for acoustic neuromas has been carried out for many years. Over time the techniques have been developed and refined greatly, and there are now three surgical approaches in use. These are called the translabyrithine, retrosigmoid and middle fossa approaches. Each has specific advantages and disadvantages.

All three types of surgery are carried out under general anaesthetic using microsurgical techniques.

At Hurstwood Park we carry out the translabyrinthine and retrosigmoid approaches. Very few centres in the UK now carry out the middle fossa approach.

What are the benefits of surgery?

The aim of surgery in most instances is complete removal of the tumour – in other words, cure. Many patients find the peace of mind that this brings of great benefit.

In some situations however we may deliberately leave behind a tiny fragment of tumour, if we feel that the chances of causing damage by removing it are too high. These small fragments may need observing with regular scans, but in our experience rarely grow and sometimes disappear.

What are the disadvantages of surgery?

Having an acoustic neuroma surgically removed is likely to mean a hospital stay of approximately 7 days. It may take up to 3 months to return fully to normal activities or return to work.

Surgery will almost certainly result in you losing any remaining hearing and balance function in the affected ear. In a very small number of cases we may be able to try to save the remaining hearing, but this depends on the size and position of the tumour and the level of hearing pre-operatively. From the point of view of balance you may well feel some increased unsteadiness after surgery, but with time your brain should adapt to this.

The hearing and balance functions of your other ear will not be affected.

What are the risks of surgery?

All surgery carries some risk. In acoustic neuroma surgery there is a risk of damage to the nerve that moves your face (facial nerve), which runs alongside the nerves of hearing and balance. Even if the nerve is not physically damaged, it’s function may be impaired. This can lead to problems affecting one side of the face varying from a mild weakness that settles down in a few weeks, to a complete permanent paralysis. The risk of this occurring depends partly on the size of the tumour. We will be able to give you an estimate of the risk of facial weakness in your own case. All acoustic neuroma surgery at Hurstwood Park is carried out using special monitoring equipment that warns the surgeon if the facial nerve is being irritated or damaged.

The nerve that provides sensation to your face (trigeminal nerve) is also close to the tumour, particularly if the tumour is large. Rarely this may be damaged, leading to numbness or tingling in parts of the face.

In order to carry out the surgery we need to make an opening in the dura, which is the tough membrane that lines the skull. At the end of the operation we need to repair this, to prevent the fluid that bathes the brain (cerebro-spinal fluid) from leaking out. We may need to take some tissue from your thigh or abdomen to do this. There is a small chance that this repair may be unsuccessful, allowing the fluid to leak out and requiring further surgery to fix it.

In any operation there is a small risk of bleeding or infection. We take great care to minimise the chances of these. However there is always a small chance of bleeding in or around the brain or of meningitis.

General anaesthetics are very safe these days, but there is a very small chance of serious anaesthetic problems and all surgery under anaesthetic carries a very small risk of death.

What are the advantages and disadvantages of the different surgical approaches?

We generally use the translabyrinthine approach as we believe it gives us the best access to the tumour and therefore the best chance of removing it completely while minimising the risk of complications. However in certain situations, particularly with larger tumours, we may use the retrosigmoid approach. We will be happy to discuss this further in clinic.

What can be done to help me with my hearing after surgery?

After surgery you will almost certainly have no hearing in the affected ear. Conventional hearing aids will not help, but there may be some ways of taking sound from the side on which you can’t hear and transferring it to your good ear. This may either involve wearing special hearing aids in both ears or using a device called a bone-anchored hearing aid (BAHA). The audiologist you see for your hearing and balance tests will be able to discuss this with you further. If you do decide to opt for a BAHA we can insert the necessary implant at the same time as your surgery.

Radiotherapy

The aim of radiotherapy, unlike surgery, is not to cure or remove the tumour, but to stop it from growing any further. The type of radiotherapy used in acoustic neuromas is very different from other types of radiotherapy you may have heard of. It involves using a highly focussed form of radiation called stereotactic radiotherapy or Gamma Knife therapy.

Unlike other forms of radiotherapy that may require a course of treatment over a number of weeks, it is given in a single dose. A special frame is attached to your head under local anaesthetic, you have a scan with the frame attached and then are given the treatment in a machine that looks rather like a large scanner.

What are the advantages of radiotherapy?

The aim of the radiotherapy is to stop the tumour from growing any further. It is successful in doing this in about 9 people in 10 (90%).

The recovery from the treatment is much quicker than with surgery. It does not require a general anaesthetic and may only require an overnight stay in hospital. As such it may be particularly suitable if you have other health problems that could increase the risks associated with surgery.

What are the disadvantages of radiotherapy?

After radiotherapy the tumour will still be present. As this treatment has only been in widespread use for just over 10 years, we do not yet know for certain whether the tumour is likely to start growing again at some point. You should therefore be prepared to undergo regular MRI scans (every year initially, then every two years) for the foreseeable future.

As this treatment requires very specialised equipment it is only performed in a small number of hospitals in the UK. This may involve you having to travel a considerable distance for your treatment.

There is about a 1 in 10 (10%) chance that the radiotherapy will not stop the tumour from growing. If this happens, surgery may be required. Carrying out surgery after radiotherapy may be more difficult and the chances of complications may be higher.

What are the risks of radiotherapy?

Other forms of radiotherapy may have side effects such as severe skin reactions and hair loss. These do not tend to be problems with Gamma Knife treatment, but some nausea may occur.

Although the radiotherapy is very accurately focussed it is inevitable that some healthy tissue, in particular the facial nerve and the nerve and organ of hearing will receive some radiation.

The chances of immediate loss of hearing or damage to the facial nerve are quite small with radiotherapy – probably less than 1 in 20 (5%). However the long term effects are less certain and the radiotherapy may do damage to healthy tissue that takes many years to show itself.

There have been questions raised about the possibility that radiotherapy could cause some acoustic neuromas to transform from benign tumours into malignant ones. There have been a small number of cases reported from around the world where this appears to have happened. We do know that in other situations in the past where benign tumours or healthy tissue have been irradiated it has taken up to 20 to 30 years for malignant changes to show themselves. As yet we do not know for certain the long-term chances of the radiotherapy given for acoustic neuromas causing malignant tumours.